Field of the Invention
The present invention relates to a wired circuit board and a production method thereof, in particular, to a method for producing a wired circuit board, and a wired circuit board produced by the method.
Description of Related Art
It has been known that a wired circuit board is produced by providing an insulating layer and a wiring pattern thereon.
For example, Japanese Unexamined Patent Publication No. 2014-127216 has proposed a method for producing a suspension board with circuit: the method includes a step of forming a first portion having a first thickness and a second portion having a second thickness that is smaller than the first thickness in the insulating layer, and a step of forming a wiring pattern so as to extend on the first portion and the second portion of the insulating layer.
To be specific, in the production method described in Japanese Unexamined Patent Publication No. 2014-127216, in the step of forming the wiring pattern, the wiring pattern is formed on the top face of the insulating layer so that the boundary between the top face and the boundary face of the first portion extends in a first direction, the side of the wiring pattern extends in a second direction crossing the first direction, and the second direction forms an angle of 60 degrees or more and 90 degrees or less relative to the first direction.
Because the boundary face is formed between the top face of the first portion and the top face of the second portion, in the step of forming the wiring pattern on the insulating layer by photo lithography technology, reflection of exposure light is caused at the boundary face, and the reflected light applies indirectly to other regions. However, in the method described in Japanese Unexamined Patent Publication No. 2014-127216, the exposure light is reflected in a direction that is close to the direction in which the wiring pattern extends at the boundary face, and therefore, the reflected light substantially does not affect the pattern of the original exposure light. Thus, breakage or short circuit is prevented in the wiring pattern formed by the photo lithography technology.